1. Field of the Invention
The present invention relates to a monitoring method carried out when a molded product is ejected from a die in an injection molding machine.
2. Description of the Related Art
In an electric injection molding machine, a molded product is ejected from a die by ejector pins incorporated in the die when it is recovered. As the product is ejected, the torque of a servomotor used as a drive source for the ejector pins is monitored. An alarm is issued if it is recognized that abnormal situation has occurred when the torque value deviates from a predetermined allowable range. More specifically, the torque of the servomotor is detected from the start to the end of the ejecting operation, and an alarm is issued if the detected torque deviates from the allowable range.
In the case of a conventional injection molding machine, the aforesaid monitoring of the ejecting load is carried out for the entire period of ejecting processes. If the shape of the product, and therefore, that of the die are complicated, for example, torque fluctuation caused as the product is ejected from the die is influenced by the positional relationship between the product and the die and the force of inertia that acts on the ejector unit as the ejecting speed changes. Accordingly, fluctuations of the ejecting load attributable to specific abnormal situations to be determined cannot be detected accurately.